Pick a tool below, or start with the ones people use most. All calculators run in your browser and are free to use.
Most popular tools
Unit Converters (8)
Translate doses between units and forms — mcg to IU, EPA/DHA concentration, extract ratios.
Dose Calculators (18)
Find an evidence-based daily dose for a single nutrient, by form and goal.
Longevity & Adaptogens (6)
NAD+ precursors, senolytics and mushroom/adaptogen dosing.
Stack Builders (8)
Combine several supplements for a goal, with per-nutrient targets.
Comparators (6)
Pick between forms or brands side by side — bioavailability, CFU, cost.
Timing & Interactions (3)
When to take things, and how to space them safely around medications.
GLP-1 & Weight Loss (3)
Cost, dose-escalation and tracking tools for Ozempic/Mounjaro users.
Quizzes & Reference (7)
Figure out what you need and how to read a label.
Frequently asked questions
Are these supplement calculators free?
Yes. Every calculator and converter on UsefulVitamins is completely free, runs in your browser, and needs no sign-up or email.
How accurate are the dose calculators?
Each tool is built from published dosing ranges and official reference values (NIH Office of Dietary Supplements, peer-reviewed trials). They give an evidence-based starting range, not a personalized prescription — confirm your dose with a doctor or pharmacist, especially if you take medication.
What is the difference between mcg and IU?
Micrograms (mcg) measure mass; International Units (IU) measure biological activity, and the conversion factor differs per vitamin. Use the Vitamin D Unit Converter or the mcg-to-IU converter to translate a label figure correctly.
Can these tools check for supplement-drug interactions?
The timing and interaction tools flag common conflicts and help you space doses. For a full check across everything you take, our companion iOS app StackMyMed scans your labels and flags interactions with source-backed warnings — always confirm anything flagged with your pharmacist.
These tools are for education and are not medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before starting, stopping, or combining supplements or medications.
